In gene therapy, intractable diseases such as genetic diseases which are due to “errors in genetic information” in cells or cancers are treated or prevented, for example, by providing correct genetic information to repair the functions of the cells, or by adding a new “protective gene” which the cells do not have originally.
A gene used as a therapeutic gene in gene therapy is usually transferred into a tissue or an organ that requires expression of the gene. This case is exemplified by therapy in which CFTR gene is transferred into respiratory epithelial cells in a patient with cystic fibrosis. In another case, a gene may be expressed regardless of tissue or organ. For example, an attempt has been made to transfer a gene encoding factor VII, which is a blood coagulation factor in plasma and is known to be produced in liver, into skeletal myocytes to produce factor VII in the cells for supplying it to plasma (Non-patent Document 1).
If there is no specific restriction concerning the cells in which the gene of interest is to be expressed like in the latter case, one may select a cell to be subjected to gene transfer (a target cell), for example, considering if the cell can be readily handled. For example, attention has been paid to use of adipocytes or preadipocytes as target cells for gene transfer because they can be readily collected, cultured and transplanted into individuals (Patent Document 1).
A method in which a target cell is infected with a retrovirus in the presence of a functional substance that binds to a retrovirus has been developed as a method for infecting a target cell with a retrovirus vector with high efficiency (Patent Documents 2, 3 and 4; Non-patent Document 2). A substance that binds to a target cell or a substance having a target cell-binding site is used in such a method. For an adipocyte or a preadipocyte, no functional substance is known to increase infectivity with a retrovirus.    Patent Document 1: WO 03/106663    Patent Document 2: WO 95/26200    Patent Document 3: WO 97/18318    Patent Document 4: WO 00/01836    Non-patent Document 1: Blood, 101:2963-2972 (2003)    Non-patent Document 2: Nature Medicine, 2:876-882 (1996)